Sin of Omission
by Lifeples
Summary: Elsa Folland was nothing more than pure, unsalvageable evil; a sadistic serial killer institutionalized in Arendelle Sanitarium. Soon escaping from the institution, she searches for her sister, Anna, who's become her obsession. Both Anna and Elsa face the dark and beautiful sides of forbidden love. This is a story about unconditional love in its sickest form. AU Modern!Frozen.
1. Chapter 1

**A/N: Okay something totally different than I normally write. A dark Elsanna fan fiction about serial killer and sociopathic Elsa who only shows emotions for her sister Anna. Everyone's ages from the Frozen film are the same in this fan fiction. Elsa being twenty-one and Anna being eighteen. Alright, I'll let you guys go.**

 **. . .**

The institution was disgustingly clean. White, pristine walls and sea green tiles that lined the floor. With the sunlight pouring through the crystal clear windows, Elsa studied the middle-aged woman who served as her therapist. She could feel her eye twitch with annoyance at the woman's chastise and content voice. Paying little mind to the woman's tedious speeches; Elsa watched the way her mouth would move or the anxious twitches she made with her hands. The tip of the woman's pencil scratching against the notebook paper, and the ticking sound of the desk clock, it all made Elsa's blood boil. The session seemed to last hours rather than minutes. She was hungry, exhausted, and bored.

Shuffling the papers aside on her metal desk, the woman abruptly stood from her chair. "That will be all, thank you Elsa." Her voice professional as she spoke.

"It was my pleasure." Elsa muttered, a depraved smile tugging at the corners of her lips.

A shiver traveled down the woman's spine, before she left the room, leaving the two police officers to unfasten the handcuffs that chained Elsa to her seat. Being yanked back onto her feet, the guards mirrored each other by standing at Elsa's sides. They effortlessly led her back to her noiseless and secluded cell. Which Elsa was thankful for. Her tolerance for the irritating therapist lady was diminishing. If she was sentenced to spend any more time with that woman, she'd use the pencil to slash open the woman's throat.

Securing the heavy metal door of her cell-room, the officers left Elsa alone to ponder in her own execrable thoughts. She gradually seated herself on the sky blue sheets of her cot. The base of her shoes touched the firm floor - while she stared blankly at a petite stain that sullied one of the four ivory walls. She let her hands descend into her lap as a memory plagued her mind.

 _"What are you doing in here?" Elsa questioned angrily at her younger sister, Anna, who'd unexpectedly barged into her bedroom._

 _"I'm worried about the puppy I found yesterday." Anna seemed small to her in that moment. Her turquoise eyes board and scared. "He's missing, I've searched everywhere." Warm tears began to cascade down Anna's freckled cheeks._

 _An unfamiliar feeling crept within Elsa. Her eyes widened momentarily, while her eyebrows shot up in fear and guilt. Fear of being caught, and guilt for hurting Anna. These were emotions that even a child her age knew, but Elsa had never experienced them before. It was foreign to her. She watched as Anna sniffled loudly and closed the door behind her as she left the room._

 _Elsa hurried over to her plastic toy box - shoving past random trinkets to reach the bottom of the box. She carefully pulled out a small object that was wrapped loosely in a grey towel. Elsa removed the urine soiled towel from the terrified puppy that was hidden underneath it. Somehow, the puppy was still alive. It's tiny chest heaving rapidly, trying to breathe in all the air it had lost._

 _Moving over to her window with the puppy in hand. Elsa slid it open and eased the puppy onto the grass outside. She quickly seized the towel from the floor and tossed it under her bed._

 _Opening her door she forged a smile and called out for her sister. "Anna, come here!"_

 _"What, what?" Anna eagerly bounced back in Elsa's bedroom._

 _Elsa pointed over to her gaping window - making Anna race past her. Anna gasped with excitement, once she saw the puppy she'd been searching for. The young girl gently picked up the puppy from outside and carried him in her hands._

 _"Olaf, you're okay." She sighed as she stroked his pale fur. "Thank you, for finding him." Anna beamed up at her sister._

 _Elsa shrugged nonchalantly. "You're welcome." She was strangely satisfied by seeing Anna happy and carefree again._

 **. . .**

Elsa's muscles flexed involuntarily under the tight restraints, that prevented her from moving even the slightest bit. Earlier the same day, in the mess hall one of the many patients waiting in line, aimed to make Elsa's life a living hell. The patient taunted and laughed as she tried hopelessly to ignore him. Her anger was seething; her fists clenching and unclenching at her sides. When he shoved his hand against her shoulder, she grabbed one of the plastic forks from the counter. Skillfully plunging the utensil into the flesh of his stomach. She twisted the fork within him - causing him to cry out in pain. In minutes the police officers hauled her away to where she was held now.

Elsa attempted to turn her head in the direction where she heard a door being shut, but the strap around her head wouldn't allow it. Looking from the comer of her eyes, she could somewhat make out a man in a white coat. The man was rummaging through multiple drawers. She continued watching from the corner of her eyes, until she saw the man hover over her.

"Hello." He greeted while calmly putting on a pair of latex gloves over his hands.

For a brief moment the man's eyes wandered over Elsa's clothed body, making her tense immensely with aggravation. Wanting to desperately lash out at him, but stopped herself before doing so.

"I highly recommend that you relax, please." He informed - settling a hand on her rigid shoulder.

A painfully, glaring light was switched on above her. Without warning a jolt of pain tore through Elsa's entire body; a surge of electricity. She desperately wanted to scream, but she was unable to. Her jaw clenched as she pressed her eyelids tightly together. Her mind was racing from one irrelevant thing to the next as the excruciating discomfort roared throughout her.

Somewhere in the far back of her depraved and detached mind, she ached for Anna's company. For the first time in her life, Elsa felt frightened and alone. Remembering when her parents had died in a car crash only three years ago. All she wanted was to be able to comfort Anna when they died, even though she didn't know how to. Elsa sank her teeth into her tongue, the coppery taste of blood filling the inside of her mouth. Unknowingly, tears crept from the creases of her closed eyes.


	2. Chapter 2

**A/N: Another chapter up for you guys. Have fun and enjoy. :)**

 **. . .**

Elsa was seated and handcuffed to one of the steel chairs, waiting for another dreary and uneventful therapy session. The door opens forcefully, though Elsa doesn't flinch at the sudden noise. She remains motionless - gazing beyond the colorless walls of the maximum security penitentiary. She expects the woman who comes in here everyday, to diagnose her with ineffective medication and worthless advice. But this time it was a short, elderly man that took the chair across from Elsa.

The man anxiously licked his lips. "Hello, I'm Dr. Sabine Weselton." He stated as he uses the sleeve of his blazer to clean the lenses of his glasses. "I am an adult physiologist, mostly for the patients here at Arendelle Sanitarium."

There's a long pause of silence, before Elsa speaks. "I'm Elsa Folland..." Her voice faint and hoarse.

"Do you remember what you and Dr. Torvik had discussed during yesterday's session?" Sabine folded his hands together, resting them comfortably in his lap. "Was it about the relationship with your parents?"

Elsa drummed her fingers in annoyance on the armrests while her features remained static. Dr. Weaselton or Weselton... whovever this new guy was; he made Elsa want to tear off her own skin. He was becoming increasingly agitating for her. His posture was composed and stoical, but the hidden fear in his blue eyes betrayed him. Elsa had always been good at reading people, they manifest their emotions through their eyes. In every pair of eyes from the countless victims she'd murdered, they would look directly into hers, exposing their desperation for life. It was arousing and intoxicating for her to see the hopelessness in them.

"What of it?" She raised an eyebrow at him.

Sabine fished out a small notepad from his coat pocket. "Were they abusive in anyway toward you?" He questioned - flipping through papers in the notepad until he came to one in particular.

"No." Elsa replied bitterly, her hand gripping onto the arm of the metal chair.

An indistinct smile flourished on Sabine's lips. He'd struck a nerve within Elsa. "It says here on your first day, you told Dr. Torvik that at the age of nine you were diagnosed with schizophrenia and antisocial personality disorder. You again stated that your parents had isolated you from others, because of these psychological disorders. Is this true?"

" _No_." Her body grew warm with rising anger, burning beneath her skin.

"They died in a horrific car accident on the twenty-first of June. Three years ago." He pushed again - hoping to provoke a flicker of weakness in Elsa. "They wanted to come home early from their trip, to surprise your sister on her birthday. Was this what motivated you to perform in a series of murders. Did you feel neglected and angry?"

Elsa took a deep breath, the poise and self-control façade was withering. "Stop trying to get in my head, it's not going to work." She muttered through gritted teeth.

"Do you believe it was your sister's fault for their tragic death?" His broad eyes were fixated on Elsa.

Sabine didn't expect to gain anything from the platinum blonde. He didn't expect to know any more than the last therapist, when he had come through the door. But he still came. Perhaps it was fascination or complete devotion to solve the scrambled puzzle pieces. To try and continue to learn what he could of her. So he waited patiently, and observed. He could see her mask gradually slipping, as he tore deeper into her concealed wounds.

Elsa always seemed lifeless, cold, and impassive to the other doctors. Not once had she made a sound, not once did she display the slightest bit of emotion. Yet now, something was stirring within her.

" _Enough_!" Her voice echoed loudly throughout the pasty room.

The aged man watched with curiosity, the way Elsa's icy-blue eyes wandered down to her hands, which were handcuffed on each side of the chair's arms. There was a sudden stiffness in her posture while her left foot jounced anxiously against the tiled floor. Sabine saw it... the small amount of panic that boiled in her. It distinctly intrigued him. However, it wasn't long before she grew still and hollow again.

Sabine cleared his throat before he stood from his seat. "Well, thank you Elsa for your time." He stuffed the tiny notepad inside his blazer's pocket and excused himself from the room - motioning to the guard he was finished.

The police officer unfastened the handcuffs and grasped Elsa's pale arm. She jerked away from his grasp and struck his nose - creating the sound of a sickening crack to bounce off the walls. Immediately, she snatched the ebony pistol that was holstered on his belt as well as his security badge. The guard collapsed on the floor with dark crimson liquid pouring from his nostrils. Tears brimmed his eyes as he stared up at her, his breath gasped in his throat. Elsa pointed the gun's barrel toward his head. She let her finger pull the trigger; soaking the floor underneath him with blood.

The ringing shot alerted the other officers in the institution. Abruptly she crept from the room and down the shadowed hallway. Bypassing the disarray of doctors, police, along with patients who were being ushered into their cells.

Gliding the security card down the systemic lock, the heavily fastened doors opened allowing Elsa to slip through. A gust of wind swept over Elsa's face when she finally made it outside of the sanitarium. She shivered violently at the feel of bitter air rushing over her skin. A roll of thunder roared loudly in the distance. Rain poured from the dark sky - drenching Elsa's platinum hair and light blue jumpsuit. She folded her arms tightly over her chest, as she ambled down the vacant road that led into the city of Arendelle. All she wanted was to see Anna again and she would; even if it meant traveling for miles in the cold and unforgiving storm.


	3. Chapter 3

**A/N: Thanks for the reviews, favorites, and follows. :)**

 **. . .**

Elsa was loitering in one of the public restrooms outside a gas station, watching the security camera, studying where it would and wouldn't catch her. If she would to linger by one of the sinks near the far corner, relatively certain that she was no longer visible to the camera. Elsa rolled her shoulders back - stretching the taut and sore muscles in her neck. She waited patiently.

The echoing sound of footsteps came from outside restroom's metal door. A man in his early twenties maybe late teens opened the door. His figure was lean and scrawny while his hair was a darker shade of blonde than Elsa's. The young man tensed slightly when he saw Elsa standing by one of the grimy sinks.

The needy itch in the back of Elsa's mind was growing increasingly hard to control. She glanced at the blonde man who appeared nervous and hesitant.

"Uh... um h-hi." He stammered, and Elsa smiled a little.

She knew her smile was unnerving. "Hi." Elsa murmured, scuffing a foot against the bathroom floor.

Her heart was thudding faster with anticipation. She felt her smile widen. Grabbing the young man's arm, he looked startled, straining to pull away. Elsa hauled him over to the handicap stall and shoved him onto the floor inside. With ease she locked the door behind them. The base of Elsa's shoe harshly slammed into the boy's windpipe - causing him to choke violently. The platinum blonde took the moment of weakness to grip the back of the boy's dark hoodie and thrust his head into the toilet.

Elsa pushed down harder on the back of his head as he started to struggle. Bubbles bursting from the surface of the toilet's water, his arms flailing blindly. She clenched her jaw and grimaced down; one hand on the back of the young man's neck while the other fisted his hair. The muscles in his chest became tight as his lungs began to burn, begging for air.

All other sounds around Elsa faded from her ears, but the frantic thrashing of water and the pounding of her own heart. She remembered the guard she'd shot. It was rushed and sloppy. It hadn't been as stimulating as this.

The boy's distraught movements grew sluggish; his arms waving uselessly at his sides. Waiting until his actions subsided and his body became still. Elsa stepped back from the blonde man's listless form, releasing her firm hold on him. The itch that crawled beneath her skin was sated... for now.

Tearing the young man's clothes from his body. Elsa quickly shed herself of the institution's jumpsuit - slipping into the dark hoodie and denim jeans. She unlocked the stall and started toward the door leading outside to the quiet gas station.

 **. . .**

 _Anna stood over the bathroom sink, her eyes tightly closed. Her breathing shallow as she cuts into her skin with a razor. A trembling gasp escapes her parted lips - opening her eyes to peer down at the crimson liquid that streams from the slit on her wrist. She stumbles backwards; lightheaded and nauseous. Her knees harshly collide with the linoleum floor as she falls._

 _Sobs quake through her entire form. Letting her eyes close yet again, she tries to think of nothing but her ragged breathes and the painful sting in her wrist. She hears the door open forcefully, but she doesn't have to open her eyes to see who it was. Anna's arms hug her midsection as she squeezes her eyelids tighter together, pretending to still be alone._

 _Elsa cautiously walks over to Anna, not wanting frighten or upset her. She kneels in front of her and gently tugging Anna's arms away from herself. Studying the fresh wound on the girl's wrist, she curiously glances down at her._

 _"What are you doing?" She raises an eyebrow at her younger sister._

 _Anna doesn't answer or open her eyes. She remains still, the slow rise and fall of her chest being the only movement. The platinum blonde sighs with impatience at the unresponsive behavior. Minutes that feel like hours surpass in silence, until Anna reluctantly opened her sore eyes to look up at Elsa._

 _"I... I miss mom and dad." She whispers, her voice breaking at the mention of their deceased parents. "I wish I'd died rather than them. Th-they didn't deserve it."_

 _Moments pass again and Anna almost thinks Elsa didn't hear her, but finally she speaks, her voice barely holding an ounce of emotion. Sending a shiver to travel down Anna's spine._

 _"Don't do this again." The narrow grip of Elsa's hand becomes painful around Anna's wrist._

 _Anna winces as she tries to pull her arm away from her sister. "El-Elsa you're hurting me." She pleads pitifully._

 _"I'm... sorry." Something dark and cold flashes behind Elsa's eyes. "I uh didn't mean to hurt you." Shaking her head sharply while she jerks her hand away from Anna._

 _Elsa exhales slowly, not realizing she'd been holding her breath until now. She pushes herself up from the ground and stands - turning toward the door. Anna abruptly rises to her unsteady feet, stopping Elsa by reaching out to grab her shoulder. Trying to form words over the lump in her throat, Anna watches through blurred vision as Elsa turns to face her._

 _Her arms wrap around Elsa's torso; burying herself against her older sister. She cried desperately, leaving Elsa entirely apprehensive and unsure on what to do. Anna's embrace tightened and Elsa could feel her shake violently._

 _When Anna pulls away she begins playing with her fingers, a nervous habit she'd developed. They stay in silence. A lonely silence they've known for so long, that it's become a comforting blanket for the both of them._

 _"I love you, so much." Anna clarifies as she wipes at the tears trailing down her cheeks. "Thank you."_

 _Elsa stares blankly at the bathroom floor, thinking. She doesn't know why the word 'love' was so hard to comprehend. Why it was so hard to comfort her younger sister when she needed her. The feeling of emptiness and lack of empathy. She wants to let Anna in, but can't. She's never cared for or been cared by somebody._

 _"I... I love you too." Her brows furrowed as the words crept from her lips._

 **. . .**

Elsa walked down the noisy aisles, listening to the rustling of people surrounding her. Parents with children in their arms as they searched throughout the grocery store. But Elsa paid little mind to the hustling customers and more so concentrated on Anna, who was placing cans of food on the shelves. Licking the crack in her lip, Elsa let out a soft chuckle as bystanders watched her with curiosity.

When Anna turned to grab another aluminum can inside a cart, Elsa could see dark circles beneath her eyes and the freckles that scattered across her nose. Her strawberry-blonde hair skillfully done in her signature braids. She looked beautifully damaged. The shouting customers, the crying children, and the silent fuming of employees. All of these petty things melted away from Elsa's mind, giving way to simple and absolute obsession. The satisfaction that everything had gotten out of her way, so she could pursue the strange palpitation in her heart whenever she saw Anna.

Elsa took a heavy breath as she pulled herself from her musings, walking through the mass of people. She paused only a few feet away from her sister. All façades vanishing in what felt like the first time in years of pretending to be humane.

"Anna." Her voice sounding foreign to her own ears.

Anna barely registered it, pretending the voice was imaginary. The haunting memories of Elsa playing in the back of her mind. She turned slowly, fear coursing through her entire form. Her turquoise eyes grew broad with horror. The distant yet familiar face of her older sister made her flesh break out in small bumps.

She swallowed thickly avoiding Elsa's blue piercing eyes as they studied her. "Elsa? H-how did you... what are you doing here?" Her tone hushed as she nervously regards the people who pass them. Anna feels the tips of her sister's fingers faintly graze her cheek, making her flinch at the gentle sensation.

"I wanted to see you." Elsa replies calmly.


End file.
